The invention relates generally to the field of devices used for secondary containment of hazardous liquid spills from primary containers such as barrels, drums, tanks, tanker vehicles, tanker trailers, railroad tanker cars, or drums or other primary containers stored on or supported by the pallets, the secondary containment devices having a reservoir or sump area to retain liquid and prevent its loss into the environment. More particularly, the invention relates to such secondary containment devices which have a reservoir with expandable capacity, and even more particularly, to such devices where the expandable reservoir reacts automatically to contain large volume liquid spills.
Hazardous liquid materials are stored in primary container means such as large drums or barrels of 30, 55 or 83 gallon capacity, large rectangular containers known as intermediate bulk containers (IBC) with capacities in the range of 120 to 600 gallons, large capacity storage tanks, tanker vehicles, tanker trailers or tanker railroad cars. Often one or more drums or containers will be placed onto a pallet for easy movement by a forklift or hand truck apparatus. Because there is a high likelihood of leakage or spillage of the liquid, secondary containment reservoir devices or pallets have been developed which retain any liquid spillage in a large volume sump area. For secondary containment pallets, regulations promulgated by the Environmental Protection Agency require the sump area to retain 100% of the volume of the single largest storage drum to be supported on the pallet, while the Uniform Fire Code requires a minimum sump area volume of 66 gallons. The containment devices generally consist of four vertical walls and a solid bottom, with some sort of support means to elevate the drums, tanks, vehicles, etc., above the sump area. This support means usually takes the form of raised ridges or column members extending upward from the bottom of the sump area, means to support a separate perforated deck or platform above the sump area, either with centrally located support columns or a peripheral support shoulder incorporated on the inside of the walls, or provisions to allow the vehicle or trailer wheels to pass into the sump area. An example of a secondary containment pallet of the type discussed above is shown in U.S. Pat. No. 4,930,632 to Eckert et al.
For circumstances where pallets are used, because the storage drums or intermediate bulk containers can be very heavy when filled and because the drums are often stored in multiples of two or four drums on a single pallet, it is difficult to design a containment pallet with sufficient strength which has the necessary sump capacity, especially when taking into consideration that the optimum design will have low side walls and a low deck height to make loading and unloading the drums safer and easier. To maximize the volume of the sump area it is also desirable to reduce the number of internal support members for the deck, meaning that a peripheral support for the deck is the preferred construction. In those containment pallets having a deck supported on a peripheral shoulder or lip located near the top of the side walls however, the compressive forces push against the side walls, causing them to bow or flex outward and eventually leading to failure of the pallet wall structure. This deflection problem was addressed in U.S. Pat. No. 5,359,955 to Grebenyuk by providing internal supports which extend from the midpoint of each side wall, creating a T-shape in horizontal cross-section. The supports extended from the bottom of the sump area to the top, the supports creating a surface onto which the deck is placed. The problem with this solution is that the supports themselves occupy a large area of the sump area, which means that the side wall height must be increased to compensate for this lost containment volume. In circumstances with large volume containers, such as tanks, tanker vehicles, tanker trailers and railroad tanker cars, the extremely large volume of liquid stored in the primary containers is so great that providing a secondary containment device with a large enough reservoir which is still accessible by the vehicles yet does not occupy a large volume of space has likewise caused difficulty.
It is an object of this invention to provide a large volume secondary containment reservoir device which has a relatively small profile or configuration, such that the device does not occupy a large space, and which includes an expandable reservoir or sump area automatically responsive to large volume liquid spills, the device being applicable for use with all types of primary containers, including but not limited to drums, barrels, IBC's, tanks, tanker vehicles, tanker trailers and railroad tanker cars. It is a further object of this invention to solve the problem of providing a large volume reservoir or sump area integral with a containment pallet without significantly increasing the overall dimensions of the pallet, thereby providing the necessary strength for support of the drums or intermediate bulk containers without recourse to extensive heightening of the side walls. It is an object to provide such a pallet which is responsive to a large volume spill with an expandable reservoir, such that the reservoir maintains a low volume configuration until needed to retain the liquid. It is a further object to provide such a pallet where the space occupied by the pallet is minimal until expansion of the reservoir. It is a further object to provide such a pallet where the expandable reservoir comprises a non-rigid bladder maintained in a coiled configuration, the bladder being self-opening in response to pressure from the liquid spill.